An FRP, particularly a carbon fiber reinforced plastic (CFRP), has come in increasingly wide use as lightweight composite material having good mechanical characteristics. A known FRP molding process comprises placing a prepreg, which is an intermediate material comprising a reinforcement fiber base impregnated with a resin, on a mold, and solidifying the resin impregnated in the reinforcement fiber base in an autoclave. Commonly, more than one prepreg sheet is piled up on the mold.
In a RTM process recently coming in wider use, however, a reinforcement fiber base comprising a woven fabric of reinforcement fibers is placed on a mold, closing a molding die, reducing the pressure in the molding die, and injecting a thermosetting resin in a flowable state or a thermoplastic resin in a flowable state into a cavity of the molding die to impregnate the reinforcement fiber base with the resin, followed by solidification of the resin (Patent Literature 1). This serves to produce high quality moldings in a short molding cycle. In cases where the resin is a thermosetting resin, the term “curing” is often used instead of the term “solidification.”
In this RTM process, a resin used to produce a molding is left and solidified at or in the vicinity of a resin injection port to the cavity of the molding die, leading to the problem of requiring a long time to remove it. To solve this problem, it has been proposed to inject the resin into the cavity through a resin tube placed at between registering surfaces of two or more molds in the molding die, and squeeze the resin tube by closing the two or more molds after the injection of the resin. When the molded product is taken out from the molding die after molding the product, the resin tube that contains solidified resin remaining inside is also removed for disposal. A new resin tube is used in the next molding cycle. This process has been proposed as a means of shortening the molding cycle by eliminating a cleaning step of the molding die (Patent Literature 2).
When using this process, however, the resin tube cannot be reused for the next resin injection because the tube pressed between the two or more molds contains resin solidified by the heat received from the molding die. Consequently, additional operations for exchange the resin tube and remove the used resin tube are required for each molding cycle, which will pose a problem. Furthermore, the resin tube for injecting resin into the cavity can be placed only to the registering surfaces of the two or more molds in the molding die. In the case of producing a molding having a shape that requires a long flow distance, for instance, a molding having a large surface, it will be difficult to shorten the step of impregnating a reinforcement fiber base with a resin, which will also pose a problem.
Patent Literature
Patent Literature 1: JP 2007-007910 A.
Patent Literature 2: JP 2005-169786 A.